This invention relates to a fiber optic security system and sensor for detecting the intrusion of a secured location and, more particularly, to such a system and sensor wherein each secured location includes a moveable closure member which secures the location and a fiber optic sensor lines routed through the sensors wherein the sensors sense movement of the closure members to an unsecured position, and the system detects the occurrence, type, and location of the intrusion.
With the increase in terrorist events needed to be prevented in the United States, the need for effective security systems to sense intrusion into secured areas has greatly increased. In particular, a security system for the protection of a vast system of underground utilities accessed by manholes with removable covers is needed. A highly effective system to detect entrance into these underground spaces and utilities is needed in order to protect against vandalization and terrorist activities within these spaces and the spaces to which these underground utilities lead. Heretofore, it has been known to use fiber optic sensors to detect theft of articles, intrusion into protected areas, as well as a variety of other purposes.
For example, U.S. Pat. No. 4,369,437 discloses a security and alarm apparatus to detect movement of a cover for a fill pipe leading to an underground fuel tank wherein an alarm signal is transmitted if the cover is disturbed. However, the system does not use fiber optics, requires electrical power at the location, and is generally not suited for a wide area security system.
U.S. Pat. No. 5,055,827 discloses an fiber optic security system to prevent the theft of appliances located in a network of computers, terminals, and associated peripheral devices. When one of the appliances is moved, light attenuation of a fiber cable results in a signal being generated. However, this system requires physical connection of the optic fiber to the appliance and the system is not suitable for detecting events in a wide geographical area.
U.S. Pat. No. 5,434,557 discloses an intrusion detection system having at least one optical cable which is usually part of a fence. When the intruder exerts force on the fence, the movement actuates a mechanical device exerting force on the cable which is detected and actuates an alarm. Here again, the system requires physical connection to the moveable part of the fence and the fiber optic cable requires electrical power at the location, and is generally not suitable for wide geographical areas.
U.S. Pat. No. 5,594,239 discloses a measuring system for monitoring buildings, train sections, or the like, consisting of a beam wave guide bending sensor. Basically, the system utilizes the deflection of a beam wave length to detect movement of the building structure.
U.S. Pat. No. 4,814,562 discloses a pressure sensor which utilizes pressure on a fiber optic in order to measure pressure.
U.S. Pat. No. 5,592,149 discloses a security fence which utilized an optical wire woven into the fence material whereupon movement of the fencing by an intruder causes the fiber wire to move and actuate an alarm signal. Once again physical connection is required between the optic fiber and the moveable closure member. U.S. Pat. No. 4,777,476 discloses another security fence wherein the optic fiber is physically connected to the moveable member to detect movement of a moveable member and intrusion to generate an alarm. U.S. Pat. No. 4,829,286 discloses yet another security fence requiring physical connection of the optic fiber to a moveable member in order to generate a signal caused by an intruder moving the fiber optic. U.S. Pat. No. 5,049,855 discloses a security screen system wherein an optical fiber is woven into the screen mesh and distortion of the screen material by an intruder causes an alarm signal.
Not only do the above security systems and sensors require a physical connection between the optic fiber and the moveable member, but the systems require electrical power at the location sought to be protected making them wholly unsuitable for many security applications, including wide geographical area systems. More importantly, no provision is made for identifying the location of an intrusion event where large numbers of sensors are utilized.
Accordingly, an object of the present invention is to provide a security system for detecting intrusion at a secured location using a fiber optic network and sensor by which the occurrence and location of an intrusion even can be reliably determined.
Another object of the invention is to provide a sensor for a securing system which generates a reliable signal for detection by an optical time domain reflectometer (OTDR) device no matter how briefly the sensor is activated.
Another object of the present invention is to provide a security system for detecting an intrusion at any one of a plurality of secured locations by an intruder using optic fiber sensor lines wherein the actuation of a sensor and determining the exact location of the sensor and the intrusion can be determined at any one of the locations.
Another object of the present invention is to provide a double-end optic fiber security system having primary and secondary units and sensor lines wherein two sensor lines run through each sensor, and in the event of a completer line break, the primary unit monitors closure members downstream of the break and the secondary unit monitors closure members on the upside of the break so that reliability is ensure in all situations.
Another object of the present invention is to provide a sensor for a security system which can be utilized with an fiber optic network requiring no electrical power and requiring no physical connection to a moveable closure member having a secured position in order to detect movement of the moveable member to an unsecured position.
Yet another object of the invention is to provide a security system using a pre-existing fiber optic network which carries voice and/or data transmissions wherein a fiber of the network may be connected to a series of sensors and to an optical reflectometer so that the occurrence and location of an intrusion may be determined.